1. Field of the Invention
The present invention relates to electronic substrates and, more particularly, to a glass laminate substrate, such as for example use in flat panel displays, wherein selected layers in the substrate include a residual compressive stress or a residual tensile stress to enhance static and impact loading resistance of the substrate.
2. Description of Related Art
Glass substrates are often used in displays, such as for example liquid crystal displays (LCDs). LCDs have become increasingly popular for displaying information in calculators, watches, video games, audio and video equipment, portable computers and even car dashboards. The improving quality and size of LCDs has made the LCDs an attractive alternative to cathode ray tubes (CRTs) which are traditionally used in television sets and desktop computer displays. In addition, other flat panel display (FPD) types, such as plasma displays (PDs), field emission displays (FEDs) and organic light-emitting polymer displays (OLEDs) are being developed as alternatives to LCDs.
In certain FPDs, two glass plates are used to carry functional layers, such as electro conductive layers for pixel addressing, color filters, liquid crystal orientation or alignment layers in LCDs or phosphor layers in FEDs and PDs. Between the two glass plates having the functional layers, a liquid crystal compound (LCDs), a light-emitting polymer (OLEDs) or a plasma-forming gas (PDs) is disposed.
The replacement of glass plates by plastic sheets is disclosed in Japanese Patent Laid-open No. 6-175143. Plastic sheets can be made thinner than glass sheets on account of their flexibility (hence providing good crack resistance) and resistance to impact and static loading. Plastic sheets also have a lower specific gravity than glass sheets, and thus an LCD with a plastic substrate is lighter and thinner than that with a glass substrate.
Unfortunately, plastic sheets have three properties that limit their application in displays: a lower glass transition temperature, a lower transmission for visible light and a higher rate of gas permeability than glass sheets. The lower glass transition temperature limits the maximum use temperature of the plastic sheet. Thus, the plastic sheets will thermally decomposed when exposed to the high, 300–600° C. temperatures required for the manufacture of a-Si or p-Si based TFTs of the kind used in LCD and OLED displays. The lower optical transmissivity reduces picture brightness. The gas permeability of a plastic sheet can lead to degradation of the organic light emitting materials used in OLED displays. Such limitations restrict the application of plastic sheets in displays.
Therefore, the need remains for a glass laminate substrate which can offer the advantages of glass sheets in conjunction with enhanced strength. The need also exists for an enhanced strength glass laminate substrate that can be formed in bulk and subsequently reduced to size without incurring significant loss due to scrap. A further need exists for a glass laminate substrate that can have reduced thickness, and hence reduced weight, while providing enhanced resistance to loading forces. A need also exists for a glass laminate substrate having a substantially predetermined resistance to impact and static loading.